Process for the manufacture of lead oxides



. instance pigments and storage battery plates.

E'atented June 15, 1933 u Nirao- -srArss-- "PATIENT OFFICE WILLIAM SCOTT 'HUTCHINSON, OF SCABSDALE, NEW YORK; EVELYN WATERS HUTCHINSON; EXECUTRIX, OF \VILLIAM SCOTT HUTCHINSDN, DECEASED, ASSIGN- OR TO WILLIAM J. PLEVIS, 01" NEW YORK, N. Y. Y

rnoonss FOR THE mnumorunn or LEAD oxxnns Application filed May 11, 1925, Serial No. 29,? 83. Renewed August 18, 1982.

This invention relates to the production of oxides of lead.

The invention relates particularly to the formation of those oxides known as litharge, niassicot and red lead. As is well known, the litb'arge and massicot are both lead monoxide, massicot being formed asthe temperature rises above the dissociation point of red lead and litliar' c being fused niassicot;

The main ob ect of my invention is to proride an improved process for producing such oxides. I

I A further object of the invention is to provide products of the character indicated having superior qualities for many uses as for pasting material for ()ther'and ancillary objects of the inven ti n will appear hereinafter.

According to the present invention, the

' lead oxides may he produced continuously from molten lead and a gas consisting largely iii: oxygen.

Present processes for the manufacture of lead oxides effect the oxidation of lead by agitation of molten material and the removal of the oxides as rapidly as possible to expose more molten metal to the oxidizing action.

All of thc present processes maintain large quantities of material in the reaction zone with the inevitable result that more heat is required to maintain the reaction tempera ture than is available from the oxidation of the lead. As a result, the oxidation is slow, incomplete and costly.

The present invention remedies this situation by subdividing the molten lead by atomization or vaporization so that the oxidation of the superficial area of any particle produces sutlicient. heat to volatilize some oxide and metal of the particle and thereby expose more metal to the oxidizing action, thus making: the process one of continuous oxidation, ilaniclihc in action and intensity.

When using air for the oxidation of lead it is found that red lead dissociates at about 545 C. and that above this temperature only the monoxide in the form of massicot or litharge may heformed. If pure oxygen is used, the tei'nperature may be raised to 630 C.

' .iww.

before red lead decomposes into massicot which will fuse into lithar e at about 888 C., the heat necessary to met the lead (which melts at approximately 327 C.) and pr0- dnce all of these substances will be provided by my method of combustion of the lead and oxygen.

There will be several advantages in substituting oxygen for air. In the first place, the heat required to heat the inert nitrogen of the atmosphere to the reaction tem era-tare will be conserved and becomes avai able for the preheating of material for subsequent oxidation. This saving in heat is immediately evidencedby a higher reaction tem- 'ieraturc. Due to the higher temperature of dissociation of red lead this increase in reaction temperature does not prevent the complction of the oxidation when properly controlled as will be later shown.

Due to the higher reaction temperature and the isolation of the oxidizing particle the .vapor tension will be greatly increased. Atthe ten'ipcratnrc of conversion of massicot into red lead in oxygen (630 C.) the vapor tension of lead is eleven times the vapor tension at the temperature of formation in air (545 0.).

In the present process the temperature of the reacting particle will flash or burn as a flame with the result that litharge is formed at an extremely high temperature a proaching the boiling point of lead (l555 The material formed will be litharge which when cooled in oxygen to (330 C. changes into red lead. The production of the red lead by cooling; as stated results in particles of much more uniform fineness than previously so that the substance is better adapted for pigments and other uses. Furthermore the fineness of the product is such that it may be used without the necessity of milling or grinding;

It is obvious thatthe oxygen alone cannot complete the oxidation spontaneously unless the lead is capable of bein converted into finely divided form with a igh partial pressure. As the temperature of the molten lend is increased the necessity for mechanical. means of atomization is decreased due to III th ta t that the vapor tension of the lead beomes an iltllYt force in converting lead lquid into lead vapor. I prefer. therefore, to llxt the heat of the reaction as tar as possible and extraneous heat in so tar as is necessary for the production of a sufliciently high vapor tension ol lead to insure its ignition in oxygen. 1

'lheoretically there are formed 229 calories per gram of lathargc and fully 75% of this is a \ailablc above 030 C. for theconversion of liquid into vapor.

In the accompanying drawing is shown liagrannnatically an apparatus by which the invention may be carried out and in connect on with which it may be illustrated.

Referring to the drawing 1 is a kettle maintained partially or completely filled with molten lead to be oxidized when starting operations. Kettle 1 is heated by any convenient source of heat, in the present case shown as a gaseous fuel from pipe 1a and be ng-burncd at burner 11). The products oi" combustion pass around kettle 1 and serve to preheat same to the kindling point of lead in oxygen. The products of combustion lina'lly escape through conduit which is controlled by valve 1r]. Valve lri is open during the preheating period and closed when the process has been properly started to prevent the loss of oxygen.

At the bottom of kettle l is a pipe 2 connected to a spray nozzle 3 for transforming the molten lead into a fine spray.

As the lead issues from 'nozzle 3 in spray form it comes in contact with the substantially pure oxygen in the chamber which ha been heated by lead oxide previously formed. The reaction between the lead and oxygen is very vigorous and takes place above C. according to the following reaction: 2Pb+ O 2Ih() =101.000 calories.

' through which oxygen is rising. There is an exchange of heat whereby the. oxygen is warmed and the PM) is cooled. As the litharge cools in contact with oxygen it (lltlflgIOS at 630 (l. toPlnt), according to the following:

GPbO QPl r10. 2,5200 calories.

The heat formed becomes available for preheating oxygen and is in addition to the ensible heat of PhD.

The solid oxides of lead formed in chamber 4 are of various particle size so that some will fall and be collected in hopper 5 from .which they may be withdrawn.

which connects to column 4. The oxygen in column 4 rises due to convection carrying with it the finer particles of lead oxide and )asses around kettle 1 which is heated there )y. This cooling serves to convert suspended litharge into red lead which is carried by the gas current through pipe 8 into settling vessel 9 where the gas current becomes snfliciently slow to allow part or all of the red lead to settle out. A further cooling of the gas in vessel 9 establishes downward convection of the oxygen and the gas circuit is completed so that it will return to column 4 and be used over again.

The red lead separating in vessel 9 collects at the bottom where it may be withdrawn through hopper 10. The oxygen returns to the system by pipe 11 entering column 4 at pointv 12. The lead oxide which settles in column 4 collects in hopper 5 and is withdrawn as required through pipe 13 and valve 14.

The means for effecting my process as shown in the drawing is merely exemplary, and it is not, desired to be confined to any specific means. The process may be practiced with improved results as applied to the production of litharge or massicot and red lead by oxidizing lead to litharge or massicot at substantially higher temperatures than are used at present, and for litharge approaching the boillng point of lead, and for massicot a temperature approaching that of formation of litharge as upper limits and then cooling the litharge or massicot in substantially pure oxygen to convert same into red lead.

Substantially pure litharge or massicot may be obtained by preventing the litharge or massicot formed in the foregoing process from cooling while subjected to oxygen, in. other words by excludlng oxygen from It while cooling.

Although it is economical to do so, my products need not necessarily be formed in an atmosphere of pure oxygen. Itis sutlicient if there is enough oxygen in the atmosphere to maintain a sufficiently high temperature to produce spontaneous combustion of lead flamelike in character. This requires a higher percentage of oxygen than is found in air and the more nearly the atmosphere is pure oxygen the more economical will be the process because of the avoidance of heating up inert elements such as the nitrogen of the air.

The oxides which are products of the process as described are extremely finely divided and of improved characteristics for numerous uses such as ingredients of paint. paste for stora battery plates etc.

While prefer to form lithargc in the first instance and then cool it to form red lead because, among other reasons, this gives a the supplied oxygen, by making the subdivision of the. lead coarser, or in other ways. .Also by suitable regulation such as'by regulating the supply of oxygen, the temperature and in other ways a mixture or blend, in the desired proportions, of red lead and monoxide. may he obtaimidfwhichi will be of superior quality because of the uniformity and fineness of the particles and homogeneousness of the mixture.

As in all other processes Where precipitation is involved, the particle size or classification will be controlled by the rate of cooling. A partial separation int-o coarse and tinevmat-erial will be effected by the rate of oxygen circulation.

While the invention hasbeen illustrated .in what are considered its best applications,

the. details of the processes recited may be varied and they may be carried out by other apparatus than that shown without departing from the spirit of theinvention. The invention is not therefor limited to the precise details of methods as recited nor to practice with the apparatnsas shown. in the raw- What l claim is:

l. A process for the production of lead oxides which comprises oxidizing finely divided loud to lead oxide and. transferring the heat of the reaction to unconibined oxygen and lead previous to their combustion .in a chemical reaction the heat transferred to the lead being atleast sufficient to maintain it in melted condition.

2. A process for the production of lead oxides which comprises oxidizing finely divided lead to litharge and transferring the heat of the reacti n to uncombined oxygen and lead previous to their combustion in a chemical reaction the heat transferred to the lead being at least suflicient to maintain it in,

melted condition.

3. A process for the production of lead ox des which comprises oxidizing vaporous lead to litharge and transferring the heat of the reaction to uncombined oxygen and lead prwious to their combustion in a chemical reaction.

ell. A process for the production of lead oxides which comprises oxidizing vaporous l ad to litharge and transferring the heat of the reaction to uncombined lead previous to combustion in a chemical reaction.

5. A process for the production of lead oxides which comprises heating lead above its melting point, contacting the lead with oxygen at a temperature at least as great as that of said melting point to produce a monoxide and cooling the monoxide in substantially pure oxygen to produce red lead.

6. A process for the production of lead oxides which comprises oxidizing lead above the temperature of dissociation of red lead and effecting an exchange of the heat of oxidation in an atmosphere rich in oxygen whereby the lead oxide is converted into a compound containing more oxygen and the uncombincd lead and oxygen are heated to substantially the boiling point of lead.

7. A process for the production of lead oxides which comprises heating lead and oxygen to substantially the temperature of boiling lead, combining lead and oxygen to form finely divided litharge, cooling said litharge by a heat exchange, preheating lead and oxygen and converting the litharge into a mixture containing red lead.

8. A process for the production of lead oxides which comprises establishingin a reaction chamber a flame of finely divided lead in oxygen, cooling the products to below the temperature of dissociation of red lead. producing a mixture containing red lead conveying said mixture into another chamber, separating the oxides from the mixture, returning the oxygen to the reaction chamber and adding more oxygen to mainta n the oxygen atmosphere. 1

-9. A process for the production of lead oxides which comprises establishing in a. reaction chamber a flame of Va porous lead in oxygen, cooling the products to below the temperature of dissociation of red lead, producing a mixture containing red lead conveying said mixture into another chamber, separating the oxides from the mixture, returning the oxygen to the reaction chamber and adding more oxygen to maintain the oxygen atmosphere. v

10. A process for the production of lead oxides which comprises producing litharge vapor and cooling the same in an atmosphere of oxygen.v

11. A process for the production of lead oxides which comprises combining lead and oxygen at a temperature above that of dissociation of red lead to produce litharge cool- 1 ing the litharge so formed and maintaining the litharge in an oxygen atmosphere untilit is cooled below the temperature of dissociation of red lead.

12. process for the production of lead oxides which comprises combining lead and oxygen at a temperature above that of dissociation of red lead to produce lead monoxide cooling the monoxide so formed and maintaining the monoxide in an oxygen atmosphere until it is cooled below the temperature of dissociation of red lead. 1

13. A process for the production of lead oxides which comprises combining lead and oxygen at a ten'iperature above that of dissociation of red lead to produce litharge cooling the litharge so formed and maintaining the litharge out of contact with oxygen until it is cooled below the temperature of dissociation of red lead.

14. A process for the production of lead 11) oxides which con'ipriscs oxidizing finely divided. lead to litharge and transferring the heat of the reaction to uncombined oxygen previous to combustion in a chemical reaction. the heat transferred to the oxygen being at least suilicient to maintain an amount of lead that will combine therewith in melted condition.

15. A process for the production of lead oxides which comprises oxidizing finely di- 50 vided lead to litharge and transferring the heat of the reaction to uncombined lead previous to combustion in a chemical reaction the heat transferred to the lead being at least sufiicient to maintain it in melted condition.

' 16. A process for the production of lead oxides which comprises oxidizing finely divided molten leadto monoxide and transferring the heat of the reaction to uncombined oxygen previous to their combustion in a 39 chemical reaction.

17. A process for the production of lead oxides whichcomprises oxidizing finely divided lead to monoxide and transferring the heat of the reaction to uncombined lead pre- Ud vious to combustion in a chemical reaction the heat transferred to the lead being at least sullicient to maintain it in melted condition.

18. A process for the production of lead oxides which comprises heating lead above its melting point, contacting the lead with oxygen at a tenuacrature at least as great as that of said melting point to produce litharge and cooling the litharge in substantially pure oxygen to produce red lead.

45 19. A process for the production of lead oxides which comprises producing litharge vapor and cooling the same in the absence of oxygen.

. 20. A process for the production of lead 59 oxides which comprises combining lead and oxygen at a temperature above that of dissociation of red lead to produce lead monoxide, cooling the monoxide so formed and maintaining the monoxide out of contact with oxygen until it is cooled below the temperature of dissociation of red lead.

In testimony whereof I have signed this specification this 8th day of April 1925.

WILLIAM SCOTT HUTCHIN SON. 

